The general principle of MPI is known from German patent application DE 101 51 778 A1. In the arrangement described in that publication, first of all a magnetic selection field having a spatial distribution of the magnetic field strength is generated such that a first sub-zone having a relatively low magnetic field strength and a second sub-zone having a relatively high magnetic field strength are formed in the examination zone. The position in space of the sub-zones in the examination zone is then shifted, so that the magnetization of the particles in the examination zone changes locally. Signals are recorded which are dependent on the magnetization in the examination zone, which magnetization has been influenced by the shift in the position in space of the sub-zones, and information concerning the spatial distribution of the magnetic particles in the examination zone is extracted from these signals, so that an image of the examination zone can be formed. Such an arrangement has the advantage that it can be used to examine arbitrary examination objects—e. g. human bodies—in a non-destructive manner and without causing any damage and with a high spatial resolution, both close to the surface and remote from the surface of the examination object.
A similar arrangement and method is known from Gleich, B. and Weizenecker, J. (2005), “Tomographic imaging using the nonlinear response of magnetic particles” in nature, vol. 435, pp. 1214-1217. The arrangement and method for MPI described in that publication takes advantage of the non-linear magnetization curve of small magnetic particles.
The application of such MPI arrangements in cardiac imaging systems has emerged as a promising market. Especially the imaging of coronaries has shown to become an important issue. In known arrangements, it has been so far difficult to image the progression of a vessel with a high resolution image. In particular for the diagnosis of a stenosis in coronary arteries, MPI arrangements of the prior art have not been ideally applicable, since an adequate solution for reconstructing a high-resolution image of a vessel from the acquired detection signals of MPI systems of the prior art is not known so far. While known MPI systems have enough temporal resolution, the spatial resolution with currently available tracer material is not sufficient to diagnose a stenosis directly.